In order to protect the functionality of known rotary lobe pumps, it is necessary to isolate fluid-free regions of the rotary lobe pump, for example areas containing gearing or bearings, from the fluid-conducting pump chamber by means of sealants. Otherwise, the penetration of liquids containing solids into the gear mechanism leads to severe signs of wear to the point of the failure of the gear mechanism after even a short period of time. In addition, the shaft and the shaft bearings must be protected against contamination by the liquid being conveyed. The region of the shaft duct from the fluid-conducting pump chamber to the fluid-free region of the pump requires special attention.
Known sealing apparatuses and known rotary lobe pumps provide for the use of sealing labyrinths in this context, which, as a contactless sealing element, make fluid transport from one side of the seal to the other side of the seal more difficult by extending the seal land, and on this basis, achieve a certain sealing action. The known sealing devices in the rotary lobe pumps do not function in a manner that is fully satisfactory, however. In the region of the base circle diameter of the rotary pistons in known rotary lobe pumps, a short-circuit current of fluid (leakage flow) from the discharge side to the suction side of the rotary lobe pump occurs at the front sides of the rotary pistons. This creates undesired piston-side wear in connection with the fiber materials being conveyed.